1. Field of the Invention
This invention relates to a method and a system for removing nitrogen and immobilized microorganisms, and more particularly to a method and a system for removing nitrogen and immobilized microorganisms, in which processing time is short and energy-saving type waste water process can be performed.
2. Description of Related Art
Nitrogen in the waste water such as drainage, excrement and industrial waste water is attributed to a cause of the eutrophication phenomenon in a closed water area such as a lake, an interior bay and the like.
A method of removing nitrogen for removing the nitrogen component from the waste water, a biological nitrogen removing process utilizing bacteria has been performed, and, as a typical example thereof, an activated sludge circulation modified method has been used. According to this biological nitrogen removing method, by utilizing oxidizing capacity of a nitrogen composed of nitrifying bacteria as being independent nutritional bacteria, firstly ammonium nitrogen in the waste water oxidized into nitrous acid and nitric acid in the aerobic condition thereafter, under the work of denitrifying bacteria as being subordinate nutritional bacteria, by utilizing the organic substance and the like in the waste water as an electron donor, nitrous acid and nitric acid are reduced to nitrogen in the anaerobic condition, whereby nitrogen is removed from the waste water.
Furthermore, as for the removal of nitrogen, it is required that the total value of nitrogen in processed water (T-N) is 10 mg/L or less, and as viewed from T-N removal rate is about 50%.
However, the conventional biological nitrogen removing method has a disadvantage in that quite a long time is required for processing and another disadvantage is, in the denitrifying reaction, since there is required a hydrogen donor such for example as methanol and hydrogen, as being an energy source of reducing power of denitrifying bacteria, processing cost is raised.
Furthermore, in the case of the conventional biological nitrogen removing method, there are required two tanks including a nitrifying tank, in which nitrifying reaction is performed in the aerobic condition and another tank, in which denitrifying reaction is performed in the anaerobic condition, whereby such disadvantages are presented that, the system is large-sized, and moreover, the provision of the two tanks necessitates an energy for circulating the waste water between the nitrifying tank and the denitrifying tank.
As described above, the conventional biological nitrogen removing method as being typified by activated sludge circulation modified method is not satisfied in the respects of the processing time, the processing cost, and making the system compact and so forth.